Relatives of Chinese passengers aboard missing Malaysia Airlines Flight MH370 watch a TV news program about the missing flight as they wait for official updates from Malaysia Airlines at a hotel ballroom in Beijing, China, Tuesday, March 11, 2014. Nearly three days after the Boeing 777 with 239 people on board disappeared en route from Kuala Lumpur to Beijing, no debris has been seen in Southeast Asian waters. (AP Photo/Alexander F. Yuan)

A Chinese relative of passengers aboard a missing Malaysia Airlines plane is surrounded by media as she answers questions about how families are being compensated outside a hotel room set aside for relatives or friends of passengers aboard the missing airplane in Beijing, China Tuesday, March 11, 2014. Authorities hunting for the missing Malaysia Airlines jetliner expanded their search on land and sea Tuesday, reflecting the difficulties in finding traces of the Boeing 777 more than three days after it vanished with 239 people on board. (AP Photo/Andy Wong)

Pictures of the two men, a 19-year old Iranian, identified by Malaysian police as Pouria Nour Mohammad Mehrdad, left, and the man on the right, his identity still not released, who boarded the now missing Malaysia Airlines jet MH370 with stolen passports, is held up by a Malaysian policewoman during a press conference, Tuesday, March 11, 2014 in Sepang, Malaysia. One of the two men traveling on a missing Malaysian Airlines jetliner was an Iranian asylum seeker, officials said Tuesday, as baffled authorities expanded their search for the Boeing 777 on the opposite side of the country from where it disappeared nearly four days ago with 239 people on board.(AP Photo/Wong Maye-E)

KUALA LUMPUR, Malaysia (AP) — Authorities are expanding their search for a missing Malaysia Airlines plane to the Malacca Strait, far from its last confirmed location, the airline said Tuesday, injecting new mystery into an investigation that so far has failed to come up with any answers.

More than three days after the Boeing 777 disappeared en route from Kuala Lumpur to Beijing, no trace of the plane has been found in waters between Malaysia and Vietnam that have been scoured by more than 40 planes and ships from at least 10 nations.

The plane, carrying 239 people, dropped off radar less than an hour into the flight without sending out a distress signal. Authorities have said it may have attempted to turn back to Kuala Lumpur, but they expressed surprise that it would do so without informing ground control.

Malaysia Airlines said in a statement that search and rescue teams expanded their scope to the Malacca Strait between Malaysia's western coast and Indonesia's Sumatra island — the opposite side of Malaysia from the plane's last known location.

To reach the strait, a busy shipping lane, the plane would have had to cross over the country, presumably within the range of radar.

An earlier statement said the western coast of Malaysia was "now the focus," but the airline subsequently said that phrase was an oversight. It didn't elaborate. Civil aviation chief Azharuddin Abdul Rahman said the search remained "on both sides" of the country.

Also Tuesday, authorities said two people who boarded the flight using stolen passports were Iranians who had purchased tickets to Europe. Their appearance on the flight had raised speculation of a possible terrorist link.

Malaysian police chief Khalid Abu Bakar said investigators had determined one was a 19-year-old Iranian, Pouria Nourmohammadi Mehrdad, and that it seemed likely he was planning to migrate to Germany.

"We believe he is not likely to be a member of any terrorist group," Khalid said.

Interpol identified the second man as Seyed Mohammed Reza Delavar, a 29-year-old Iranian, and released an image of the two boarding a plane at the same time. Interpol Secretary General Ronald K. Noble said the two men traveled to Malaysia on their Iranian passports, then apparently switched to their stolen Austrian and Italian documents.

He said speculation of terrorism appeared to be dying down "as the belief becomes more certain that these two individuals were probably not terrorists." He appealed to the public for more information about the two.

Malaysia Airlines, meanwhile, said it is investigating an Australian television report that the co-pilot on the missing plane had invited two women into the cockpit during a flight two years ago.

Jonti Roos described the encounter on Australia's "A Current Affair." The airline said it wouldn't comment until its investigation is complete.

Roos said she and her friend were allowed to stay in the cockpit during the entire one-hour flight on Dec. 14, 2011, from Phuket, Thailand, to Kuala Lumpur. She said the arrangement did not seem unusual to the plane's crew.

"Throughout the entire flight, they were talking to us and they were actually smoking throughout the flight," Roos said.

Roos didn't immediately reply to a message sent to her via Facebook.

The missing plane took off from Kuala Lumpur, on the western coast of Malaysia, early Saturday en route to Beijing.

It flew across Malaysia into the Gulf of Thailand at 35,000 feet (11,000 meters) and then disappeared from airport radar screens.

China, where two-thirds of the passengers are from, urged Malaysian authorities on Tuesday to "speed up the efforts" to find the plane. It has sent four ships, with another four on the way.

The United States has sent two Navy ships, at least one of which is equipped with helicopters, and a Navy P-3C Orion plane with sensors that can detect small debris in the water.

Vietnamese planes and ships are also taking part. Lt. Gen. Vo Van Tuan, deputy chief of staff of the Vietnamese People's Army, said authorities on land have also been ordered to search for the plane, which could have crashed into mountains or uninhabited jungle. He said military units near the border with Laos and Cambodia had been instructed to search their regions also.

"So far we have found no signs ... so we must widen our search," he said.

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